1. Field of the Invention
The present invention relates to a vehicle headlamp system adapted to control the beams emitted from headlamps.
2. Description of the Related Art
Typical conventional vehicle headlamps are incapable of sufficiently irradiating road surfaces ahead of a vehicle when the vehicle is driven on mountain roads, around curves at intersections, and so forth, because the beam emitting directions are fixed.
In this connection, JP-A-6-72234 discloses a vehicle headlamp system adapted to detect a vehicle speed and a road configuration ahead of one""s own vehicle, and to calculate a position that the vehicle is expected to reach after being driven for a predetermined time in accordance with the road configuration, with the calculated arriving position of the vehicle as a target position.
In the vehicle headlamp system of the above-described publication, however, there exists the following problem. Although the actual vehicle speed (the vehicle speed at a point of the present time) is taken into consideration when one""s own vehicle position a predetermined time later is calculated, no consideration is given to variation in the vehicle speed owing to the road configuration ahead of the vehicle.
More specifically, when the traveling road ahead of the vehicle is a curved road, the vehicle speed tends to become lower than that on a straight road. Also, the vehicle speed on a sharply curved road tends to become lower than that on a moderately curved road. Consequently, when the arriving position of one""s own vehicle is estimated with the actual vehicle speed as a reference, the actual arriving position of one""s own vehicle may largely differ from the estimated value. Such an error in the arriving position of one""s own vehicle makes it infeasible to sufficiently irradiate the road surface ahead of the vehicle.
An object of the present invention, made in view of the foregoing circumstances, is to provide a vehicle headlamp system for controlling beams from headlamps by accurately estimating the arriving position of one""s own vehicle a predetermined time later, which arriving position is used as a target position for beam control.
In order to accomplish the above and other objects, the arriving position of one""s own vehicle is estimated on the basis of an advisable vehicle speed corresponding to the radius of curvature of a traveling road ahead of a vehicle by calculating the radius of curvature thereof.
A vehicle headlamp system according to the invention comprises:
headlamps for emitting beams forward from a vehicle, and beam control means for controlling the beams emitted from said headlamps,
road-configuration detection means for detecting a road configuration ahead of the vehicle; and
means for estimating the arriving position of one""s own vehicle a predetermined time later,
wherein said beam control means performs said beam control with said arriving position of one""s own vehicle as a target position, and
wherein said means for estimating the arriving position of one""s own vehicle calculates the radius of curvature of a traveling road ahead of the vehicle from the results detected by said road configuration detection means so as to estimate the arriving position of one""s own vehicle on the basis of an advisable vehicle speed corresponding to the radius of curvature thus calculated.
The contents of the beam control performed by the xe2x80x98beam control meansxe2x80x99 are not limited to specific ones, but may include any suitable contents for variable control over, for example, the direction of the beam emitted from each headlamp, the emission range of the beam emitted therefrom, and the emitted quantity of light, or a proper combination thereof.
The xe2x80x98road configuration detection meansxe2x80x99 is not limited to specific contents for detection, but may be any suitable means such as a navigation unit and a CCD camera capable of detecting a road configuration ahead of a vehicle.
The xe2x80x98advisable vehicle speedxe2x80x99 is a vehicle speed at which the vehicle is driven in a curve safely and pleasantly, and is preset in accordance with the radius of curvature of the traveling road.
xe2x80x98On the basis of the advisable vehicle speedxe2x80x99 means using the advisable vehicle speed as one of the parameters when the arriving position of one""s own vehicle is estimated and, needless to say, the actual vehicle speed (i.e., vehicle speed at the present time), which is different than the advisable vehicle speed, may be used as one of the parameters.
As described above, the vehicle headlamp system is adapted to perform beam control with the arriving position of one""s own vehicle the predetermine time later as the target position, which predetermined time is estimated by the means for estimating the arriving position of one""s own vehicle. However, the means for estimating the arriving position of one""s own vehicle is also adapted to calculate the radius of curvature of a traveling road ahead of the vehicle, from the results detected by the road configuration detection means, so as to estimate the arriving position of one""s own vehicle on the basis of an advisable vehicle speed corresponding to the radius of curvature thus calculated. Therefore, the following operation/working effect is achievable.
More specifically, when the arriving position of one""s own vehicle is estimated with only the actual vehicle speed as a reference, the actual arriving position of one""s own vehicle may greatly differ from the value estimated in accordance with the road configuration ahead of the vehicle. However, provided the arriving position of one""s own vehicle is estimated on the basis of the advisable vehicle speed corresponding to the calculated radius of curvature of the traveling road ahead of the vehicle, the arriving position of one""s own vehicle can accurately be estimated by taking into consideration a variation in vehicle speed that is likely to occur in the near future.
In the vehicle headlamp system so arranged as to perform beam control over the headlamps according to the invention, there accurately can be estimated the arriving position of one""s own vehicle the predetermined time later, which is the target position of beam control, whereby the road surface ahead of the vehicle is sufficiently irradiated.
The xe2x80x98predetermined timexe2x80x99 is not specifically limited, but is preferably set within the range of values from 1.5 to 3.5 seconds and, more preferably, is set within the range of values from 2 to 3 seconds (e.g., 2.5 seconds) in order to sufficiently irradiate the road surface ahead of the vehicle.
The xe2x80x98predetermined timexe2x80x99 may be set at a fixed value, and may also be subjected to increase/decrease correction according to the difference between the advisable vehicle speed and the actual vehicle speed. With the adoption of the latter, the estimated accuracy of the arriving position of one""s own vehicle can be prevented from being reduced when the advisable vehicle speed is not observed on the traveling road ahead of the vehicle.
The arriving position of one""s own vehicle is shifted to a position farther than the estimated position as the actual vehicle speed grows greater than the advisable vehicle speed. Then, an increase/decrease correction is preferably made such that the predetermined time is set shorter as the actual vehicle speed becomes greater than the advisable vehicle speed.
The turning radius of the actual turning travel line may often have different values when the traveling road ahead of the vehicle is a rightward-turning road, and where the traveling road is a leftward-turning road. Therefore, the arriving position of one""s own vehicle is preferably estimated by setting the predetermined time at different values depending on whether the road ahead of the vehicle is the rightward-turning or the leftward-turning road.
More specifically, the predetermined time on the rightward turning road may be set at a value greater than the value set on the leftward turning road in the keep-to-the-left traffic environment. Similarly, the predetermined time on the leftward turning road may be set at a value greater than the value set on the rightward turning road in the keep-to-the-right traffic environment.